Search

SUMMARYA new strain of Trigonella foenum-graecum has B-chromosomes indistinguishable from chromosomes of regular complement. Study of carrier plants revealed that both somatic and meiotic carrier cells have 2B chromosomes. In PMCs the 2B chromosomes pair to form a bivalent that behaves normally during meiosis. The carrier cells of root, shoot, leaf and petal tips show 18 chromosomes besides 16 chromosomes in non carrier cells. Genetic mechanism ensuring 2Bs in the carrier cells is discussed. Their regular meiotic behaviour, indistinguishable and euchromatic nature, indicate comparatively recent origin. It has been found that the plants having lower B frequency in the PMCs have lower average values of its various parts and vise versa. There is a random distribution of chromosomes in the various plant parts but the interesting point to note is that the total mean values of carrier cells in PMCs, shoot tips, leaf tips and root tips of all carrier plants is almost the same.

SUMMARYCuttings of 2x and 4x Ruellia species, their 2x, 3x and 4x hybrids were irradiated at 2, 4 and 6 Krad of gamma rays (CO60). Radiosensitivity of the above genotypes in relation to ploidy and hybridity was studied using the parameters like sprouting of cuttings, survival, growth reduction, final height, number of branches and pollen fertility. Differences in sensitivity of different species of the same ploidy level were noticed. Tetraploids in general, were radioresistant. Hybridity increases the resistance of diploid hybrid above that of its parents. Polyploid hybrids were intermediate to their parents in radioresistance and the cancellation of the negative and positive effects of the alleles has been suggested as the probable reason for it. ICV (interphase chromosome volume) of all the species and hybrids was determined and the possible correlation of ICV with radiosensitivity is discussed.

SUMMARYComparative radioresistance of diploids and artificially raised tetraploids of Trigonella foenum-graecum has been investigated at 30 and 50 krad of gamma rays. Advantage of using autoploids for such studies have been discussed. Different parameters were taken into consideration. Germination in both cases show little effect of radiation. Despite higher ICV, at higher doses, 4 n were resistant in survival, growth reduction at maturity and pollen sterility. Seed setting in 4 n was severely affected. Differential response of 2 n and 4 n in chiasma frequency at different doses was noted. A possible correlation between higher frequency of abnormal cells, univalents, Lagging chromosomes, fragments in 4 n with higher ICV has been proposed.

SUMMARYInheritance of B-chromosomes in the selfed progeny of plants of Trigonella foenumgraecum possessing 1, 2 and 3 Bs was investigated. Plants having 0,1 and 2 Bs were noted in the progeny of IB parent while the progeny of plants possessing IB, 2Bs and 3Bs had 0,1 and 2 Bs; 0,1,2 and 3 Bs; and 0,1 and 3 Bs respectively. It appears that 3Bs in maximum dose of tolerance in the strains under investigation. These studies also threw light on possible mode of origin of extra chromosomes.

SUMMARYArtificially raised tetraploids in Tropaeolum majus enhanced its ornamental value. Octoploids, though had smaller flowers but umbrella shaped appearance of leaves make them quite charming. Ploidy barrier exists in the species. Tetra and octoploids were perfectly seed sterile despite good pollen fertility in tetraploids. Lack of dehiscence of anthers was noted in tetraploids but artificial pollination also failed to achieve seed setting. The pollen grain germinated normally on 4n stigma and also pollen tube travelled down through the stylar tissue. In rare cases fruit formation was initiated but after some growth they aborted and their study revealed total absence of developing embryos. Efforts to overcome ploidy barriers have been discussed.

SUMMARYThe chromosome number of Citrus Assamensis has been found to be 2n — 18. Though it is ordinary diploid species yet it shows multivalent formation ranging from trivalent, quadrivalent to esavalent. The bridge fragment configuration has also been observed at anaphase. The second division is marked by stray chromosomes and laggards. The pollen sterility is 45%.

SUMMARYThe comparative effects of colchicine in combination with 11 chemicals (1 paradichlorobenzene, 2 coumarine, 3 saponin, 4 α-bromonapthalene, 5 phloroglucinol, 6 8-hydroxy-quinoline, 7 gammexane, 8 aesculine, 9 acenapthene, 10 β-bromonapthol and 1l phenol) on the production of polyploid cells in Trigonella foenum-graecum has been studied. In the chemicals alone in comparison to water the root growth has been accelerated in (1), (7) and (9) while (5) shows no change and in the rest there is a decrease. In Combination with colchicine every chemical shows decrease except in (3), and 10. The frequency of metaphase plates per root tip is lowest in water while it reaches the maximum in (3) followed by (4), (8), (5), (7), (6), (9), (1), (10) and colchicine in decending order. In combination with colchicine the accumulation of metaphase plates increases in (1) while in the rest there is a decrease. The rate of root growth and karyokinetic activity are not interrelated to each other. There is some correlation...